The present invention relates to a novel class of boride-based refractory and abrasive bodies or, more particularly, to a class of refractory and abrasive bodies based on certain metal diborides as sintered with high density and high mechanical strengths even at elevated temperatures and also to a method for preparing the same.
With their extremely high melting points and hardness as well as excellent mechanical strengths at elevated temperatures, metal diborides such as titanium diboride are the most promising materials for construction of rockets, cutting tools, parts of thermal engines and the like. When metal diborides are to be sintered for use in these applications, however, difficulties are encountered because the sintering temperature is extremely high and the sintered bodies obtained are sometimes poor in the bending strengths and relatively brittle regardless of whether the metal borides are used either singly or as a combination of two kinds or more.
One of the inventors conducted extensive investigations to solve the above problems in the sintered refractory bodies of metal diborides and discovered that titanium diboride or other metal diborides could give improved sintered bodies when admixed with an alloy of nickel and phosphorus (see, for example, Japanese Patent Disclosure 52-106306).
These titanium diboride-based sintered bodies as developed above possess a bending strength reaching 100 to 150 kg/mm.sup.2 but, needless to say, even higher bending strengths are sometimes required in the practical use of these kinds of refractory materials. In addition, the heat resistance of the above developed titanium diborite-based refractory materials is not always satisfactory due to the use of a nickel-phosphorus alloy with a relatively low melting point down to 890.degree. C.
Accordingly, further investigations have been undertaken resulting in a discovery that admixture of nickel borides, iron borides and/or cobalt borides as a binder ingredient with a combination of at least two kinds of metal diborides instead of the nickel-phosphorus alloy can give much improved sintered refractory bodies (see, for example, Japanese Patent Application 54-36398 corresponding to a copending U.S. application Ser. No. 89,487).
The present invention has resulted from the works as an extension of the above investigations with the object to obtain metal diboride-based sintered refractory bodies with further improved or more reproducible mechanical properties, especially, at elevated temperatures.